As it has been revealed that formation of active oxygen species in the living body and accompanying formation of peroxylipid have a variety of adverse influences on the living body through membrane disorder or enzyme disorder, various attempts have been made to apply lipid peroxidation inhibitory agents to pharmaceuticals. Currently, as, lipid peroxidation inhibitory agents used in the pharmaceutical field, derivatives of natural antioxidants such as vitamin C, vitamin E and β-carotene, etc. and phenol derivatives are mainly known (authored by Kenji Fukuzawa, Nippon Rinsho vol.46, pp 2269-2276, 1988 and Sies, H., Stahl, W., Sundquist, A. R., Ann. N. Acad. Sci., vol.669, 7-20, 1992). However, these have insufficient activities and have side effects and, therefore, they are not necessarily satisfactory practically.
On the other hand, JP-A-52-23096 discloses, as a furo[2,3-f]quinoline derivative, a quinoline carboxylic acid derivative represented by the formula: wherein R1 is an unsaturated, straight or branched alkyl group having 1 to 6 carbon atoms and R2 is hydrogen or a saturated or unsaturated, straight or branched alkyl group having 1 to 6 carbon atoms, and a physiologically acceptable salt with an inorganic or organic base when R2 represent hydrogen atom, a method for preparing the same and an agent for treating a urinary tract infection containing the same, together with a typically exemplified compound represented by the formula: and the like.
JP-A-50-117908 discloses a veterinarian antibacterial formulation comprising as an effective ingredient a quinolone carboxylic acid derivative represented by the formula: wherein A is an alkylene group having 2 to 3 carbon atoms (provided that this alkylene group may contain 1 or 2 oxygen atoms at the terminal or halfway of its carbon chain), and this alkylene group is bound to two adjacent carbon atoms on the benzene ring; R1 is hydrogen atom or amino group, and R2 is a lower alkoxy group, a lower aminoalkyl group or a lower alkenyl group when R1 is hydrogen atom, while R2 is an alkyl group when R1 is amino group, together with a typically exemplified compound represented by the formula: and the like.
JP-A-50-117909 discloses an agent for preventing or treating ichthyic bacterial diseases containing as an effective ingredient a quinolone carboxylic acid represented by the formula: wherein A is an alkylene group having 2 to 3 carbon atoms (provided that this alkylene group may contain 1 or 2 oxygen atoms at the terminal or halfway of its carbon chain), and this alkylene group is bound to two adjacent carbon atoms on the benzene ring; R1 is hydrogen atom or amino group, and R2 is a lower alkoxy group, a lower aminoalkyl group or a lower alkenyl group when R1 is hydrogen atom, while R2 is an alkyl group when R1 is amino group, together with a typically exemplified compound represented by the formula: and the like.
JP-A-47-1081 discloses a method for preparing a quinoline carboxylic acid represented by the formula: wherein each of R and R1 denotes hydrogen atom or an alkyl group, and A denotes a divalent group: wherein X, Y and Z are taken together to form a dihydrofuran ring such that —X—Y—Z— is —O—CH2—CH2— or CH2—O—CH2— and wherein a ring formed by X, Y and Z may be substituted with 1 to 3 oxo groups, and a salt thereof with an inorganic or organic base, together with a typically exemplified compound represented by the formula: and the like.
JP-A49-30369 discloses a method for preparing a quinoline carboxylic acid derivative represented by the formula: wherein R1 is a lower alkyl group, which comprises reacting a 1-hydroxy-4-quinolone 3-carboxylic acid derivative represented by the formula: with an alkylating agent to form a quinoline carboxylic acid derivative represented by the formula: wherein R1 is as defined above, followed by hydrolyzing, together with a typically exemplified compound represented by the formula: and the like.
European Journal of Pharmacology (1988), 346(2/3), 175-180 discloses as a furo[2,3-f]indole derivative having an antidepressive activity a compound represented by the formula: 
A lipid peroxidation inhibitor (antioxidant) which has a lipid peroxidation inhibitory activity based on an excellent antioxidative effect and which exhibits an excellent pharmacokinetic profile is expected to exhibit an excellent effect in prophylaxis or therapy against a central nerve system disease (for example, ischemic central nerve disease (e.g., cerebral infarction, cerebral hemorrhage, cerebral edema), central nerve damage (e.g., cranial trauma, spinal damage, whiplash), neurodegenerative disease (e.g., Alzheimer's disease, Parkinson's disease, Huntington's chorea, amyotrophic lateral sclerosis), vascular dementia (e.g., multi-infarct dementia, Binswanger's disease), manic-depressive, melancholia, schizophrenia, chronic pain, trigeminal neuralgia, migraine and the like), a circulatory system disease or failure (for example, ischemic heart disease (e.g., cardiac infarction, angina pectoris), arterial sclerosis, post-PCTA (percutaneous transluminal coronary angioplasty) arterial restenosis, lower urinary tract disease or failure (e.g., dysuria, urinary incontinence) and the like), diabetic neurosis and the like.
Nevertheless, a fully satisfactory substance has not been identified yet, and thus a compound having an excellent lipid peroxidation inhibitory activity and which is fully satisfactory as a pharmaceutical is expected to be developed.